Derivatives of thiophosphoric acid



United States Patent DERIVATIVES 0F THIOPHOSPHORIC ACID Walter Lorenz,Wuppertal-Elberfeld, Germany, assignor to Farbenfabriken BayerAktiengesellschaft, Leverkusen, Germany, a corporation of Germany NoDrawing. Application July 17, 1956 Serial No. 598,257

Claims priority, application Germany February 26, 1953 1 Claim. (Cl.260-248) The present invention relates to new derivatives ofthiophosphoric acid and to a process of making the same; moreparticularly the invention is concerned with compounds of the generalformula in which alk stands for an alkyl radical having 1-2 carbonatoms.

The new compounds can be obtained by reacting N-halogenomethyl-benzazimides, which may be substituted in the benzenenucleus with the salts of dialkylthio-phosphoric acids. The reaction ispreferably carried out in an inert diluent. Suitable diluents accordingto the invention are especially ketones but alcohols or other solventssuch as benzene or toluene may also be employed. This application is acontinuation-inpart of my application S. N. 487,458, filed February 10,1955 (now Patent No. 2,758,115), which latter application is in turn acontinuation-in-part of my application S. N. 411,025, filed February 17,1954 (now abandoned).

Due to the high reactivity of N-halogenomethylbenzazimides the reactionstarts already at room temperature; it is advantageous, however, tocomplete the reaction at slightly elevated temperatures.

The N-halogenomethylbenzazimides employed as starting products for theprocess of the invention are obtainable from the corresponding methylolcompounds with the aid of halogenating agents in known manner.

The compounds obtained according to the invention are either solid,crystalline substances having a low melting point or non-distillable,water-insoluble oils. The new compounds obtained in accordance with theinvention are highly effective against sucking and chewing insects,especially against spider mites. The new compounds are, therefore, veryvaluable plant protecting agents.

In the following some reactions are described by way of example toillustrate the method of preparing N- methylolbenzazimide and,therefrom, N-halogenomethylbenzazimides which are used as startingmaterial to obtain the insecticidal compounds contemplated by theinvention.

PREPARATION A N-methylolbenzazimide (N-hydroxymetizyl-benzazimia'e) 250grams of benzazimide are slightly heated with 1.6 liters of 30%formaldehyde and 300 ml. of water while stirring on the water bath forminutes. The mixture solidifies to a viscous paste. By filtering thepaste with suction the methylol compound is obtained in almostcolourless needles. M. P.: 134-135 C; yield: 277-300 grams, i. e.92-100% of the theoretical.

2,843,588 Patented July 15, 1958 Alternatively, the methylol compoundcan be obtained by dissolving the benzazimide, which is still wet fromits manufacture, with twice the quantity of a 30% formaldehyde solutionand eight times the quantity of water on the water bath, filtering thesolution with some charcoal and allowing the solution to cool. The yieldof N-hydroxymethyl-benzazimide is almost quantitative.

PREPARATION B N -ch loromethyl-b enzazimide 700 grams (4 mols) of dryN-hydroXymethyl-benzazimide are suspended in 1.5-2 liters of chloroform.1.8 mols (about 130 ml.) of thionylchloride are added rapidly, thetemperature rising to 35 C. Another quantity of thionylchloride, 3.8mols (about 270 ml.), is run in so as to obtain a temperature of 40-50C. The mixture is stirred at 60-65 C. for one hour, the residueseparated by filtering and the solvent distilled off. The solidifiedresidue is dissolved in 1 liter of acetone and the solution is pouredinto 4 liters of water with vigorous stirring to prevent the chloridefrom precipitating in clots. The mixture is filtered with suction, thefilter cake washed until free from acid and the resultingN-chloromethylbenzazimide dried in air. M. P.: 124 C.; yield: 590-700grams, i. e. -89% of the theoretical. By recrystallizing from 10 timesthe quantity of isopropyl alcohol the product is obtained in an entirelypure condition; M. P. 125

PREPARATION C N-bromomethyl-benzazimia'e 53 grams ofN-hydroxymethyl-benzazimide are suspended in 250 ml. of acetonitrile.33.6 grams of phosphorus tribromide are added dropwise at 20-30 C. withcooling. After stirring at room temperature: for one hour the mixture ispoured into water, the reaction product filtered with suction and Washedwith water. The felted needles are crystallized from some metha-noL- M.P.: 126 (3.; yield: 20 grams.

The following examples are given to illustrate the invention without inany way limiting the same.

EXAMPLE 1 A solution of 20 grams of N-chloromethylbenzazimide in 200 cc.of methylcthylketone is added at 50 C. drop Wise to 24 grams of theammonium salt of 0,0-diethyl-- thiophosphorie acid in cc. ofmethylethylketone. The solution is heated at 70-80 C. for two hours, thepre cipitated ammonium chloride is filtered ofl after cooling and thesolvent distilled in vacuum. The remaining oil is taken up in benzene,washed with water and dried over sodium sulfate. After distilling offthe solvent 0,0-diethyl-S-(benzaziminomethyl)-thiolphosphate is obtainedas a red-brown colored, non-distillable oil. The yield amounts to 21grams.

EXAMPLE 2 24 grams of N-bromo-methyl-benzazimide (M. P. 137- 139 C.) and18 grams of the ammonium salt of 0,0- dimethyl-thiolphosphoric acid aresuspended in 100 cc. of acetone at room temperature. The temperaturerises slowly to about 30 C. while the N-bromo-methyl-benzazimidedissolves. Thereafter the reaction mixture is stirred for one hour atroom temperature and then 2 hours at 50-60 C. The precipitated ammoniumbromide is filtered off. From the filtrate the acetone is distilled offin vacuo, thus yielding 30 grams (100% of the theoretical) of0,0-dimethyl-S-(benzaziminomethyl)-thiolphosphate. The product obtainedcan be recrystallized from isopropyl alcohol or from diluted methanol orbenzene by adding ether M. P. 81-83 C.

3 4 I claim: References Cited in the file of this patent The compoundhaving the formula UNITED STATES PATENTS 2,758,115 Lorenz Aug. 7, 1956 C0 O OH: 5

i'/ FOREIGN PATENTS H, 927,270 Germany May 2, 1955

